fix(visibility): Look for field meta on data['meta']['fields']

[gggritso]

Discover responses look like this:

{
  data: [
    {
      'eps()': 0.01087819860850493,
    },
  ],
  meta: {
    fields: {
      'eps()': 'rate',
    },
    units: {
      'eps()': '1/second',
    },
  }
}

You can see that field types are on the meta.fields object. However, the field renderers look for field types like this:

const fieldType = meta[fieldName] || meta.fields[fieldName];

They're just looking for keys on meta itself! This is because Discover data fetchers do this:

const {fields, ...otherMeta} = data.meta ?? {};
return {
  ...data,
  meta: {...fields, ...otherMeta},
};

I don't know why! I'm curious to know why. However, regardless of why, field renderers should attempt to find field definitions on the data.meta.fields object, if it exists. This makes it easier to use field renderes on Discover responses regardless of context (e.g., in the new data visualization widget components)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
static/app/utils/discover/fieldRenderers.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #77951      +/-   ##
==========================================
- Coverage   78.12%   78.12%   -0.01%     
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  Files        6995     6995              
  Lines      310205   310219      +14     
  Branches    50760    50763       +3     
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+ Hits       242352   242359       +7     
- Misses      56133    56138       +5     
- Partials    11720    11722       +2